The Kremlin-backed candidate for Mayor of Moscow won the first round election on Sunday, but opposition leader and anti-corruption blogger Alexei Navalny says the vote was suspect and he got enough to force a run-off.

Initial 'official' results seemed to show Vladimir Putin’s ally Sergei Sobyanin just topping the 50 percent barrier needed to win outright.

But Navalny is vowing not to allow a “single vote be stolen”.  His campaign team has exit polling indicating Navalny got 35 percent instead of the 27 percent the Kremlin claims, and that Sobyanin had fallen short of the 50 percent mark, meaning the two should face each other in a runoff.

Voter turnout in the Moscow Mayoral election was a low 33 percent.  That helps Navalny, whose energized, young supporters turned out in droves, compared to the low mobilization of elderly, more conservative voters apt to support the Kremlin.

A pro-Navalny rally is planned Monday evening on the same Moscow square where he helped lead anti-Putin protests that erupted following allegations of widespread fraud in a December 2011 parliamentary election won by Putin's ruling party.